This invention relates to circuit breakers in general and more particularly to an improved compressed gas circuit breaker.
Compressed gas circuit breakers with two contacts and a nozzle-like insulating body, which are arranged coaxially and are movable relative to each other in the direction of their axis are known. The insulating material body serves, along with pressure springs, as a stop for closing off the gas flow canal. At least one of the contacts, generally, is designed in the shape of a hollow cylinder with a nozzle-shaped entrance. The arc drawn in such puffer or two-pressure breakers when the contacts are opened is blasted essentially radially by the flow of quenching gas due to the nozzle shape of the insulating material body in conjunction with the hollow cylindrical contact.
In one known compressed gas circuit breaker with contacts movable in the axial direction and designed in nozzle-fashion, a valve which can be controlled by the onset of the gas flow toward the quenching gap, is provided in the gas stream. A piston, which compresses the gas in a space underneath the piston, is fastened to the movable contact. A nozzle-like body of insulating material, which surrounds the quenching gap, serves as a stop for closing off the gas flow canals. In the closed condition of the breaker, the canals are closed off by a ring through the force of pressure springs which are designed so that during an opening operation, the body of insulating material is lifted from the flow canals against the spring force at a predetermined pressure of the quenching gas, and releases the gas flow to the quenching gap. As the gas pressure increases steadily, the flow canals open accordingly. The damger of oscillations, the damping of which requires special measures, is therefore not precluded (German Offenlegunsschrift No. 2,336,684).
In another known compressed gas circuit breaker, the quenching gas flow sets in when the contacts have already travelled a predetermined part of their opening distance. The quenching chamber contains a movable switching pin and an annular fixed contact which is surrounded by a cylinder of insulating material. The blasting piston is provided with a follower piston which partially encloses the movable breaker contact, closes off the stationary cylinder of insulating material from the puffer piston in the closed condition of the breaker and protrudes from the stationary cylinder during the opening, and thereby releases the gas flow only when the movable contact has travelled at least one quarter of its total opening distance. The gas flow is substantially axial to the arc. The breaker is therefore suitable only for relatively small currents (Swiss Pat. No. 409,060).